Containment aerosol characterization during nuclear power plant severe accident

ABSTRACT

The aerosol size distribution and concentration during a postulated severe accident scenario were simulated using a numerical code NAUA to characterize the aerosols dispersed in the containment under various conditions. The model-predicted aerosol concentration and particle size distribution were in general agreement with the measured data reported in previous studies. A large set of sensitivity tests were conducted to examine the effects of input parameters. The main particle removal mechanism in containment was gravitational sedimentation when wall temperature was assumed to be the same as the air temperature, whereas diffusiophoresis became a more important particle removal mechanism when the difference between the wall temperature and air temperature was significant. The operation of a containment filtered venting system (CFVS) resulted in reduced particle concentration, mass median diameter (MMD), and geometric standard deviation (GSD) because aged larger particles were removed by the CFVS. The particle concentration and GSD of the containment aerosol decreased with increasing emitted particle size owing to the effect of gravitational sedimentation that removes large particles selectively. Non-sphericity of particles reduced the particle removal rate due to gravitational sedimentation, leading to higher particle concentration, MMD, and GSD.

KEYWORDS:

• Aerosol dynamics modeling
• nuclear reactor accident
• radioactive aerosol